It is well known that drugs can directly react with excipients. In addition, excipients can be a source of impurities that either directly react with drugs or catalyze their degradation. Thus, binary mixtures of three diuretics, torasemide, furosemide and amiloride with different excipients, i.e. citric acid anhydrous, povidone K25 (PVP), magnesium stearate (Mg stearate), lactose, D-mannitol, glycine, calcium hydrogen phosphate anhydrous (CaHPO4) and starch, were examined to detect interactions. High temperature and humidity or UV/VIS irradiation were applied as stressing conditions. Differential scanning calorimetry (DSC), FT-IR and NIR were used to adequately collect information. In addition, chemometric assessments of NIR signals with principal component analysis (PCA) and ANOVA were applied. Between the excipients examined, lactose and starch did not show any interactions while citric acid, PVP, Mg stearate and glycine were peculiarly operative. Some of these interactions were shown without any stress, while others were caused or accelerated by high temperature and humidity, and less by UV/VIS light. Based on these results, potential mechanisms for the observed interactions were proposed Finally, we conclude that selection of appropriate excipients for torasemide, furosemide and amiloride is an important question to minimize their degradation processes, especially when new types of formulations are being manufactured.